Method of preparing iron ore fine bearing materials for metallurgical purposes



METHOD OF PREPARING IRON ORE FINE BEAR- NGEMATERIALS FOR METALLURGICAL PUR- OS S Joseph Becker, Pittsburgh, Pa., assignor to Koppel-s Company, Inc., a corporation of Delaware No Drawing. Application June 4, 1953, Serial No. 359,655

6 Claims. (Cl. 7 --4) The present invention relates to an improvement in the process of utilizing iron-ore-fines bearing materials wherein such materials are mixed with coals destined for coking chambers. More particularly, the present invention re.- lates to an improvement in this process by mixing such materials to a limited portion of the total charge of coals destined for coking chambers.

In the prior art, it is known that iron-ore-fines bearing materials such as blast furnace flue dust can be utilized by mixing such materials with the entire quantity of coals destined for coking chambers. By so mixing, valuable ores, carbonaceous matter and the like present in the materials and which might otherwise have been wasted are retained in the coke produced, to be utilized with this coke ash in turn is utilized for various metallurgical purposes. However, the presence of iron in the mixture of the iron-ore-fines bearing material and the coal has resulted in increasing the percentage of sulfur retained in the coke produced, causing a decrease in the value of the coke. for subsequent metallurgical purposes. This is particularly so when the coke is used in blast furnaces. For example, an increase in the percentage of sulfur in the blast furnace charge necessitates an increase in the amount of limestone which accompanies such a charge. Moreover, the presence of iron in the mixture of the ironore bearing fines and coal has resulted in decreasing the coke by-product yields of ammonia and tar. This loss of marketable ammonia and tar results in lower credits for these by-products with resulting higher costs of the coke produced.

One of the features of the present invention is to provide an improved process of utilizing iron-ore-fines bearing materials by mixing them with coal destined for coking chambers in such a manner that the average sulfur content in the coke produced from a total charge of coal will be reduced.

Another feature of the present invention is to provide an improvel process of utilizing iron-ore-fines bearing materials by mixing them with coal destined for coking chambers in such a manner that the deleterious effects of the iron charged with the coal on the overall coking by-product yields are greatly reduced.

Still another feature of the present invention is to provide a process of utilizing iron-ore-fines bearing materials by mixing them with coal destined for coking chambers in such a manner that the yields of ammonia and tar from the majority of the coking ovens will be unaffected.

More particularly, the present invention provides an improved process of utilizing iron-ore-fines bearing materials comprising the steps of dividing a total coal charge destined for coking chambers into major and minor portions, mixing said iron-ore-fines bearing materials with the minor portion of said total coal charge destined for coking chambers so that said minor portion of said total coal charge will contain a large percentage of iron-orefines bearing materials, and the remaining major portion of said total coal charge will be straight coal, separately tet r 2,801,913 3C6 Patented Aug. 6, 1957 coking said portions of said total charge, and using said coked portions conjointly for metallurgical purposes.

The percentage of the portion of coal that is mixed with iron-ore-fines bearing materials to the total coal charge can range from about 5% to about 45% and in a preferred embodiment of the invention ranges from about 8% to about 25%.

In carrying out the present invention, the quantity of iron-ore-fines, such as taconite, magnetite or hematite ore fines or blast furnace flue dust, which is mixed with a minor portion of the total coal charge destined to be coked can vary from approximately 20% to approximately iron-ore-fines in the coke oven charge.

As aforementioned, the mixing of blast furnace flue dust or other iron-ore-fines with only a minor portion of the total coal to be charged to the coking ovens and the subsequent coking of this mixture in a few ovens, instead of spreading the iron-ore-fines throughout the total charge to be coked in all ovens as heretofore known in the art, has resulted in reducing the average sulfur in the coke produced.

This is illustrated by the following two examples which compare the old method of incorporating iron-ore-fines bearing material with coal to produce metallurgical coke (Example 1), with the present inventive method (Example 2):

Example 1 88 tons of ore fines are combined with 1430 tons of coal having a sulfur content of 1.2%. This charge is coked according to ordinary coking procedures for the production of metallurgical coke. There is obtained a product of which approximately 1000 tons is coke derived from the coal. The total sulfur content of the product is 1.61% based on the 1000 tons of coke.

The original coal contained 17.16 tons of sulfur which in ordinary coking operations (that is without the incorporation of iron-ore-fines) would result in about 30% (5.15 tons) appearing in the off gases as H28. However, when ore dust is used, of the H28 ordinarily obtained is retained in the final coke product and only 20% appears in the off gases as HzS. That is, 1.03 tons of sulfur appear as hydrogen sulfide and 16.13 tons of sulfur remains in the coke.

Example 2 1430 tons of coal having a sulfur content of 1.2% is coked together with 88 tons of iron-ore-fines as follows:

The 88 tons of ore dust is mixed with 205 tons of coal and this mixture is coked according to ordinary coking procedures for the production of metallurgical coke separately from the remaining 1225 tons coal. There is obtained from the coking of coal mixed. with ore fines a product containing approximately 144 tons coke. This product has a total sulfur content of 1.61% based on the 144 tons of coke. There is obtained from the coking of the 1225 tons coal approximately 856 tons coke having a sulfur content of 1.2% and the ammonia and tar recovery is that usually obtained in ordinary coking and by-product recovery operations.

The two coked products when used conjointly as a metallurgical coke have an average sulfur content of 1.26%. This coke can be used in charging a blast furnace with excellent results being obtained.

The original coal which was mixed with the ore fines contains 2.46 tons sulfur. Of this, 0.15 ton appears in the off gases as H2. The 1225 tons of coal contain 14.70 tons sulfur of which 4.41 tons appear in the off gases as H28. Thus, according to the above procedure, 4.56 tons of sulfur appear as H28 as compared to only 1.03 tons as per Example 1 and only 12.6 tons of sulfur appear in the total coke produced.

These two examples demonstrate that sulfur content of the coke is reduced from 1.61% according to known methods to the desirable percentage of 1.26% according to this invention.

The total coke produced by a process like that set forth in Example 2 is then used for some metallurgical purpose. For example, the total coke produced may be fed to a blast furnace.

Although it has been stated that the two products can be used conjointly for some metallurgical purpose, it will be realized that the two products can. be mixed prior to such use, if so desired. It is not necessary that the two types of coke be intimately mixed for purposes of this invention. For example, the two types of coke can be charged to a furnace in layer fashion.-

It is noted that the addition of pitch to the mixed portion of iron ore fine bearing materials and coal serves to further improve the quality of coke produced by the aforedescribed inventive process, and in one embodiment of the invention, a pitch range of 3-15% of mixed portion of pitch, coal and flue dust is maintained.

'It is further noted that the coking temperatures used in carrying out the present invention are substantially the normal coking temperatures used in by-product coke ovens, it being advisable to limit the coke oven wall temperatures to a maximum of 2150 F. in order to avoid attack of the coke oven refractory by flue dust. Byproduct'coke ovens such as shown in U. S. Patent No. 2,498,784 are'especially useful in the practice of the present invention. l

It will be obvious to one skilled in the coking art that various changes can be made in the several steps of the process disclosed herein Without departing from the scope or spirit of'this invention.

The invention claimed is:

l. An'imp'roved process of utilizing iron-ore-fines bearingmaterials comprising the steps of dividing a total coal charge destined for high temperature lay-product coking chambers intomajor and minor portions, mixing said iron-ore-fines bearing materials with said minor portion of said total coal charge so that said minor portion of said total coal charge will contain a large percentage of iron-ore-fines bearing materials and the remaining major portion of said total coal charge will be straight coal in order to reduce the average sulfur content in the total coke produced from said total charge and to maintain unaifected yields of ammonia and tar from the majority of by-product coking chambers in which said total charge is coked, separately coking said portions of said total charge, and using said coked portions conjointly for metallurgical purposes.

2. The process of claim 1, wherein said minor portion of said total coal charge ranges from about 5 to about 45%.

3. The process of claim 1, wherein said minor portion of said total coal charge ranges from about 8% to about 25%.

4. The process of claim 1, wherein said minor portion of said total coal charge is mixed with iron-ore-fines bearing material in such proportions that the mixture contains 20%6S ore fines.

5. An improved process of utilizing iron-ore-fines bearing materials comprising the steps of dividing a total coal charge destined for high temperature by-product coking chambers into major and minor portions, mixing said iron-ore-fines bearing materials with said minor portion of said total coal charge so that said minor portion of said total coal charge will contain a large percentage of iron-ore-fines bearing materials and the remaining major portion of said total coal charge will be straight coal in order to reduce the average sulfur content in the total coke produced from said total charge and to maintain unaffected yields of ammonia and tar from the majority of by-product coking chambers in which said total charge is ooked, adding pitch to the mixed portion of ironore-fines bearing materials and coal, separately coking said portions of said total charge, and using said coke portions conjointly for metallurgical purposes.

6. The process of claim 5, wherein said pitch ranges from about 3% to about 15% of the. mixed portion.

References Cited in the file of this patent UNITED STATES PATENTS 803,792 Sheldon Nov. 7, 1905 FOREIGN PATENTS 2,607 Great Britain of 1866 3,314 Great Britain of 1876 4,639 Great Britain of 1914 OTHER REFERENCES The Making, Shaping and Treating of Stee (6th edition), page 345. 

5. AN IMPROVED PROCESS OF UTILIZING IRON-ORE-FINES BEARING MATERIALS COMPRISING THE STEPS OF DIVIDING A TOTAL COAL CHARGE DESTINED FOR HIGH TEMPERATURE BY-PRODUCT COALING CHAMBERS INTO MAJOR AND MINOR PORTIONS, MIXING SAID IRON-ORE-FINES BEARING MATERIALS WITH MINOR PORTION OF SAID TOTAL COAL CHARGE SO THAT MINOR PROTION OF SAID TOTAL COAL CHARGE WILL CONTAIN A LARGE PERCENTAGE OF IRON-ORE-FINES BEARING MATERIALS AND THE REMAINING MAJOR PROTION OF SAID TOTAL COAL CHARGE WILL STRAIGHT COAL IN ORDER TO REDUCE THE AVERAGE SULFUR CONTENT IN THE TOTAL COKE PRODUCED FROM SAID TOATL CHARGE AND TO MAINTAIN UNAFFECTED YIELDS OF AMMONIA AND TAR FROM THE MAJORITY OF BY-PRODUCT COKING CHAMBERS IN WHICH SAID TOTAL CHARGE IS COKED, ADDING PITCH TO THE MIXED PORTION OF IRONORE-FINES BEARING MATERIAL AND COAL, SEPARATELY COKING SAID PORTIONS OF SAID TOTAL CHARGE, AND USING SAID COKE PORTIONS CONJOINTLY FOR METAILURGICAL PURPOSES. 